Mark R J, Hensley K, Butterfield D A, Mattson M P
Sanders-Brown Research Center on Aging, University of Kentucky, Lexington 40536, USA.
J Neurosci. 1995 Sep;15(9):6239-49. doi: 10.1523/JNEUROSCI.15-09-06239.1995.
The amyloid beta-peptide (A beta) that accumulates as insoluble plaques in the brain in Alzheimer's disease can be directly neurotoxic and can increase neuronal vulnerability to excitotoxic insults. The mechanism of A beta toxicity is unclear but is believed to involve generation of reactive oxygen species (ROS) and loss of calcium homeostasis. We now report that exposure of cultured rat hippocampal neurons to A beta 1-40 or A beta 25-35 causes a selective reduction in Na+/K(+)-ATPase activity which precedes loss of calcium homeostasis and cell degeneration. Na+/K(+)-ATPase activity was reduced within 30 min of exposure to A beta 25-35 and declined to less than 40% of basal level by 3 hr. A beta did not impair other Mg(2+)-dependent ATPase activities or Na+/Ca2+ exchange. Experiments with ouabain, a specific inhibitor of the Na+/K(+)-ATPase, demonstrated that impairment of this enzyme was sufficient to induce an elevation of [Ca2+]i and neuronal injury. Impairment of Na+/K(+)-ATPase activity appeared to be causally involved in the elevation of [Ca2+]i and neurotoxicity since suppression of Na+ influx significantly reduced A beta- and ouabain-induced [Ca2+]i elevation and neuronal death. Neuronal degeneration induced by ouabain appeared to be of an apoptotic form as indicated by nuclear condensation and DNA fragmentation. The antioxidant free radical scavengers vitamin E and propylgallate significantly attenuated A beta-induced impairment of Na+/K(+)-ATPase activity, elevation of [Ca2+]i and neurotoxicity, suggesting a role for ROS. Finally, exposure of synaptosomes from postmortem human hippocampus to A beta resulted in a significant and specific reduction in Na+/K(+)-ATPase and Ca(2+)-ATPase activities, without affecting other Mg(2+)-dependent ATPase activities or Na+/Ca2+ exchange. These data suggest that impairment of ion-motive ATPases may play a role in the pathogenesis of neuronal injury in Alzheimer's disease.
在阿尔茨海默病中以不溶性斑块形式在大脑中积聚的β-淀粉样肽（Aβ）可直接具有神经毒性，并可增加神经元对兴奋性毒性损伤的易感性。Aβ毒性的机制尚不清楚，但据信涉及活性氧（ROS）的产生和钙稳态的丧失。我们现在报告，将培养的大鼠海马神经元暴露于Aβ1-40或Aβ25-35会导致Na+/K(+)-ATP酶活性选择性降低，这发生在钙稳态丧失和细胞变性之前。暴露于Aβ25-35后30分钟内，Na+/K(+)-ATP酶活性降低，到3小时时降至基础水平的40%以下。Aβ不会损害其他Mg(2+)-依赖性ATP酶活性或Na+/Ca2+交换。用哇巴因（一种Na+/K(+)-ATP酶的特异性抑制剂）进行的实验表明，该酶的损伤足以诱导[Ca2+]i升高和神经元损伤。Na+/K(+)-ATP酶活性的损伤似乎与[Ca2+]i升高和神经毒性有因果关系，因为抑制Na+内流可显著降低Aβ和哇巴因诱导的[Ca2+]i升高及神经元死亡。哇巴因诱导的神经元变性似乎是凋亡形式，表现为核浓缩和DNA片段化。抗氧化自由基清除剂维生素E和没食子酸丙酯可显著减轻Aβ诱导的Na+/K(+)-ATP酶活性损伤、[Ca2+]i升高和神经毒性，提示ROS起作用。最后，将死后人类海马体的突触体暴露于Aβ会导致Na+/K(+)-ATP酶和Ca(2+)-ATP酶活性显著且特异性降低，而不影响其他Mg(2+)-依赖性ATP酶活性或Na+/Ca2+交换。这些数据表明，离子驱动ATP酶的损伤可能在阿尔茨海默病神经元损伤的发病机制中起作用。
